1. Field of the Invention
The present invention relates generally to a lighting device with larger projection angle and projection range.
2. Description of the Related Art
There is a trend toward energy saving and carbon reduction in the field of lighting equipments. Accordingly, the conventional tungsten filament bulbs have been gradually replaced with light-emitting diodes for saving power.
The light-emitting diode has the advantage of energy saving. However, the projection angle of the light emitted from the light-emitting diode is relatively small. This is because the lighting angle of the light-emitting diode is simply about 120 degrees due to its own luminous properties. Therefore, in the case that the light-emitting diode is assembled with a light tube without property of diffusion, the lighting angle of the light-emitting diode can be hardly enlarged.
In many application situations, clients desire that the luminous properties of the light-emitting diode lamp tube are as similar to the luminous properties of the conventional fluorescent lamp tube as possible. Therefore, most of the light-emitting diode lamp tubes are made of materials with diffusion effect. In this case, on one hand, the luminous properties of the light-emitting diode lamp tube are more similar to the luminous properties of the conventional fluorescent lamp tube and on the other hand, the glare of the lighting device can be minimized.
In general, even if a diffusion agent is added, in comparison with the conventional lamp tube, the lighting angle of the light-emitting diode is still narrower. The ratio of the diffusion agent can be increased to achieve larger lighting angle. However, under such circumstance, the permeability will be greatly decreased. Accordingly, the conventional lighting device has the following shortcomings:
1. Smaller projection angle.
2. Poor permeability.
3. Smaller projection range.